1. Field of the Invention
This invention relates to a method of monitoring the production of clothing fabric, and in particular to a method of monitoring the production of fabric for use in protective clothing.
2. Discussion of the Prior Art
When producing protective clothing for the military, a variety of chemicals, e.g. charcoal, latex and flame retardant are applied to the clothing fabric. Typically, application is effected by dipping the fabric in solutions or slurries of the chemicals, and passing the fabric between squeeze rolls to control the quantity of chemical added to the fabric. In the present case, the aim is to control the quantity of charcoal added to the clothing material. The quantity of charcoal incorporated in the fabric must be monitored and controlled in order to ensure that the clothing provides adequate protection.
At present, the quantity of charcoal added to fabric is controlled by two methods, either or both of which may be used at one time. The first method involves the weighing of one hundred meter rolls of material before and after passage through a charcoal bath and squeeze rolls. A figure representing the average concentration of charcoal in the entire roll is obtained from the equation: ##EQU1##
The second method involves the cutting of small pieces of material from the untreated material, and then passing the material through the charcoal bath and between the squeeze rolls. Additional small pieces are cut from the fabric adjacent to the first "cuts" and of identical size. The quantity of charcoal added to the material is calculated using the above equation.
The above described measuring methods are not without shortcomings. The first method relies on a number of assumptions. Firstly, it must be assumed that the starting material, i.e. the fabric to be impregnated is uniform in terms of weight per unit area. It has been found that the foam laminate presently used in protective military clothing may vary in weight from batch to batch. Thus, if the weight of the untreated material is considered to be a constant, then errors in the calculation of the quantity of added charcoal will occur. Other factors can affect the quantity of chemical added to the fabric during each impregnation operation. It has also been found that if all parameters are kept constant, the quantity of added material can increase constantly through an impregnation operation. Thus, even though the average value obtained using the first method is indicative of acceptable material, there could be large areas of fabric which are unacceptable in terms of charcoal content. Such areas would be detected during the more detailed testing of quality control. However, the problem cannot be corrected after the material has been dried and cured.
For the most part, the above comments are equally applicable to the second method. Taking small samples or templates as representative of an entire roll of material could be extremely misleading, because of the cyclic nature of the adding of the chemical under constant processing conditions and the inherent variations in the base material. The second method also requires destructive sampling of the base material.
The object of the present invention is to overcome the problems encountered using present measuring techniques by providing a relatively simple, accurate method of determining the quantity of chemical being added to a fabric on a continuous basis.